Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/10577#discussion_r49631656
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala
---
@@ -170,17 +173,27 @@ object ExtractFiltersAndInnerJoins extends
PredicateHelper {
}
}
+
/**
* A pattern that collects all adjacent unions and returns their children
as a Seq.
*/
object Unions {
def unapply(plan: LogicalPlan): Option[Seq[LogicalPlan]] = plan match {
- case u: Union => Some(collectUnionChildren(u))
+ case u: Union => Some(collectUnionChildren(ArrayBuffer(u),
Seq.empty[LogicalPlan]))
case _ => None
}
- private def collectUnionChildren(plan: LogicalPlan): Seq[LogicalPlan] =
plan match {
- case Union(l, r) => collectUnionChildren(l) ++ collectUnionChildren(r)
- case other => other :: Nil
+ @tailrec
+ private def collectUnionChildren(
+ plan: ArrayBuffer[LogicalPlan],
--- End diff --
We can just use `push/pop` or `enqueue/dequeue` instead of `tail`, although
it's not so functional...
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